Date	Event	Description
9 March 2016	New search has been performed	The review has been updated. Specifically we have: Added three further trials. Amended text of abstract, results and discussion to reflect the new material. Updated discussion to include more contemporary references. Updated the study flow diagram. Re‐formatted and updated the summary of findings table. Re‐formatted the results section, removed text references to single trial analyses and replaced with results from the original papers. We deleted the sensitivity analyses for single trials.
9 March 2016	New citation required but conclusions have not changed	The current update includes substantial changes in presentation and content, but the conclusions are unchanged.
29 March 2012	New citation required but conclusions have not changed	Searches re‐run March 2011 and three new studies identified.
11 January 2012	New search has been performed	'Risk of bias' and 'Summary of findings' tables added. Study flow figure added. No major change to conclusions
23 August 2008	New search has been performed	Two new trials identified and added to review when searches were re‐run in August 2008.
26 April 2008	Amended	Converted to new review format.
23 May 2005	New citation required and conclusions have changed	Substantive amendment